[ppml] alternative realities (was PIv6 for legacy holders (/wRSA + efficient use))
peter at boku.net
Thu Aug 2 12:20:18 EDT 2007
...or you'll be black-holed if your Cogent line is down while your other
ISP's circuit is alive and kicking.
Multi-homing in that reality becomes hit and miss. It's not worth paying
any fees to the second ISP if anyone who wants to reach you is sitting
behind a filtering ISP. The funny part is that they lose you as a customer
based on policy enacted by a non-related entity.
On 8/2/07 11:06 AM, "Scott Leibrand" <sleibrand at internap.com> wrote:
> Does Cogent have a route to your /24? Do they announce a covering
> aggregate? If so, then you will retain reachability even to networks
> who filter your /24, via Cogent's aggregate..
> Steven E. Petty wrote:
>> I'm not certain your assumptions are valid. I know my workplace is
>> currently multihomed using a /24 assigned from cogent in the 38. This
>> filter would remove my routes. Under current ARIN policies, our two
>> dozen or so hosts don't qualify us for a direct assignment/allocation
>> despite multi-homing.
>> -----Original Message-----
>> From: Scott Leibrand [mailto:sleibrand at internap.com]
>> Sent: Wednesday, August 01, 2007 8:08 PM
>> To: Paul Vixie
>> Cc: ppml at arin.net
>> Subject: Re: [ppml] alternative realities (was PIv6 for legacy holders
>> (/wRSA + efficient use))
>> If someone can come up with a helpful policy, I'm all ears. But yes, I
>> do think this kind of thing will be self-correcting, for one simple
>> reason: you don't have to know who's doing it to filter effectively.
>> All you need to know is what the minimum allocation size for each
>> address range is. (I know you know all this already, but I'm sure there
>> are others who don't.) A quick look at
>> http://www.iana.org/assignments/ipv4-address-space and
>> http://www.arin.net/reference/ip_blocks.html gives me a pretty good idea
>> that I could filter, more or less safely, anything larger than /8 in the
>> 0/8 to 56/8 range (with a couple exceptions, like down to /20 in 24/8),
>> down to /16 in the 128/8 to 172/8 range, down to /20 in the 63/8 to 99/8
>> range, etc. If I were to implement such a policy, I'd first take a good
>> hard look at my BGP table (rather than the cursory look I just did), but
>> it's by no means necessary to identify the specific players doing the
>> deaggregation in order to appropriately filter it.
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